In recent years, multimedia communications over the Internet and/or other wired and/or wireless multimedia communications network(s) have gained increased popularity. Such multimedia communications can be performed within the context of video communications systems, such as video conferencing systems, video calling systems, video transcoding systems, video playback systems, interactive voice and video response (IVVR) systems, etc. In video communications, transmissions of video data from video data senders are typically based on the real-time transport protocol (RTP), and deliveries of such video data to video data receivers are typically monitored using the real-time transport control protocol (RTCP). For example, such video data receivers that receive video data in the form of RTP packets from one or more video data senders can provide reception quality feedback information to the respective video data senders in one or more RTCP report packets. Further, such video data senders can estimate available bandwidths of the respective video data receivers using at least the reception quality feedback information provided in the RTCP report packets, and, if desired and/or required, adjust their video data transmit rates so as not to exceed the estimated available bandwidths of the video data receivers.
Such multimedia communications can be problematic, however, particularly when transmissions of multimedia data including video data are performed over multimedia communications networks such as the Internet. For example, while the video data senders transmit video data over the Internet, various participants in the video communications may be subjected to varying levels of network congestion, which can result in changes in the available bandwidths of at least some of the video data receivers. Such network congestion that results in changes in the available bandwidths of the video data receivers can be caused by increases and/or decreases in bandwidths employed by other participants in the video communications, changes in physical locations of mobile participants in the video communications, certain errors occurring within the multimedia communications network, etc. Moreover, if the video data senders transmit video data at transmit rates that exceed the available bandwidths of one or more of the video data receivers, then the respective video data receivers may experience increased packet losses. Alternatively, if the video data senders transmit video data at transmit rates that are below the available bandwidths of one or more of the video data receivers, then reduced video quality may be exhibited at the respective video data receivers. In either case, the video quality of experience (QoE) may be degraded for at least some of the video data receivers participating in the video communications.
It would therefore be desirable to have improved systems and methods of performing multimedia communications over multimedia communications networks, in which video data senders can more reliably maintain high video QoE levels despite changes in available bandwidths of video data receivers.